Bourdon tube gage assembly



June 27, 1967 c. J. FOLTZ BOURBON TUBE GAGE ASSEMBLY Filed Feb. 10, 1965 INVENTOR. CHARLES J. FOLTZ BY ATTORNEY United States Patent 3,327,534 BOURDQN TUBE GAGE ASSEMBLY Charles J. Foltz, Havertown, Pa., assignor to the United Eatates of America as represented by the Secretary of the Navy Filed Feb. 10, 1965, Ser. No. 431,747 1 Claim. (Cl. 73-418) ABSTRACT OF THE DISCLOSURE A tube assembly located within a housing and formed of a Bourdon tube which communicates at one end with an exterior source of pressure and has its other end tapered and providing a confined open end. A closed end tube attachment having a confined passageway is connected by an exterior ring weld to the tapered open end of the Bourdon tube to provide a smooth inner surface and prevent the accumulation of deposits.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The problem of cleaning Bourdon tube gages and maintaining such gages in properly operating condition is well known and the prior art has been successful in overcoming the problem to a degree which is satisfactory for use with certain types of equipment or in certain processes. When such gages are used, for example, with oxygen systems on naval vessels, it is requisite that they be maintained free of contaminants such as oil in order to eliminate the existence of explosive or other hazardous conditions.

One approach which has been used is to provide the closed end of the Bourdon tube with a valved opening whereby pressure may be applied to the tube when desired for the removal of entrapped air or other contaminants. This approach has not been satisfactory for cleaning gages used in the oxygen systems of naval vessels for the reason that the valved opening of the Bourdon tube requires threaded connections which may form areas causing the entrapment of contaminants and increase the likelihood of explosive or hazardous conditions. Another objection to their use is that the added weight of the valve structures adversely affect the desired vibration characteristics of the gage. Consequently, Bourdon tube gages having threadedly connected valve arrangements are not sanctioned for use on naval vessels.

In order to overcome the problems of air and oil entrapment and the above mentioned objections, it is proposed that a close-d end auxiliary tube having a confined passageway relative to the diameter of the Bourdon tube be permanently attached to the movable end of the Bourdon tube and that the auxiliary tube be of substantial length permitting the end portion to be severed in order to provide access thereto for the application of pressure to the Bourdon tube. It is requisite that the auxiliary tube have its open end welded or brazed into the extreme or tip end of the Bourdon tube and in a manner to provide a smooth connection with the inner surface of the Bourdon tube in order to completely evacuate the Bourdon tube and also to minimize or eliminate zones for oil entrapment. With the Bourdon tube modified in this manner, the end of the auxiliary tube will, after its end portion is severed, be again closed and the severing and closing operation repeated a number of times providing an expedient arrangement for maintaining a gage in proper operating condition. The auxiliary tube will preferably be incorporated in the form of a helix to permit its being located within a confined area of the gage housing.

The principal object of this invention is to assemble a cleansing attachment to the tube of a Bourbon tube gage which permits thorough removal of entrapped contaminants and yet does not adversely effect the gage operation.

Another object of this invention is to provide a Bourbon tube gage construction having an auxiliary tube fixedly connected to the tip end of the Bourbon tube in a manner to provide continuous uninterrupted inner surfaces in the tube assembly.

Still another object is to provide such a gage construction having an auxiliary tube welded to the tip end of the Bourbon tube in a manner to provide continuous uninterrupted inner surfaces in the tube assembly.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings, wherein.

FIGURE 1 is an elevational view of a Bourbon tube gage embodying the invention with the rear face of the gage removed to show details of operating structure.

FIGURE 2 is a pictorial view in partial section showing a detail of FIGURE 1.

Referring to FIGURE 1, a cylindrical gage casing or housing is indicated at 10 and is shown with its back cover removed and having a pressure inlet connection 12, for example, as extending through the side wall of the casing. The inlet 12 will be connected to a pressure source which is not shown but may be considered to be an oxygen system of a submarine nuclear power plant, the pressure of which is to be measured and indicated. The Bourbon tube of the gage is indicated at 14 and has an open fixed end 16 communicating with the inlet 12 and a movable end portion 18 spaced from the fixed end.

The front face of the housing 10 has a graduated scale, which is not shown, and an indicator 20 movable relative to the scale in accordance with deflections of the movable portion 13 of the Bourdon tube through connections as is well known in this art. The present arrangement, as shown, is to fixedly mount the indicator 20 for movement with a rotative pinion 22 which in turn is operative through a rotative actuator 24 having a gear segment end 26 in mesh with pinion 22 and a slotted end portion 28. A link arm 30 has one end pivotally connected to the slotted end portion 28 through an adjustable pin 32 and its other end pivotally connected at 34 with an arm 36 which is welded to the movable end portion 18 of the Bourdon tube.

The movable or free end 18 of the Bourdon tube is modified by the present invention over known disclosures of the prior art by the addition of a tube 38 which has a closed outer end portion 40. The tube 38 may be termed a capillary tube since it will have a passageway or diameter which is small or confined relative to that of the passageway of the Bourdon tube 14. The tube 38 communicates directly with the movable end portion 18 of the Bourdon tube but due to the small diameter of its confined passageway the movement of the tube 38 is unaffected by pressure passing thereto from the Bourdon tube 14 and consequently its movement is controlled by movement of the free end 18 of the Bourdon tube.

In assembling the gage, the Bourdon tube 14 will be provided with a small aperture at the tip end of the free end portion 18 which is tapered as shown to form the small aperture and the capillary tube 38 will be welded or soldered thereto by an exterior ring weld con nection. The welding or soldering operation will be effected in a manner to provide a smooth or continuous inner surface as shown in the sectioned portion of FIG- URE 2 in order to prevent the formation of any areas where contaminants may become entrapped.

The invention is applicable to both high and low pressea /353a sure gages and since the invention concerns the welding or soldering of the tubes together it is essential that the tubes be constructed of the same metal or metals which are compatible and can be so connected. The Bourdon tube is preferably of elliptical shape in order to provide proper movement of its movable end portion while the auxiliary tube may conveniently be cylindrical. A Bourdon type commercial gage was modified in accordance with this invention by the application thereto of a 0.032" diameter capillary tube and operated effectively in gaging pressures of upwardly of 5000 pounds. Cleaning of the gage was accomplished by flushing the tube assembly with Freon solvent followed by passing dry nitrogen through the assembly.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that, within the scope of the appended claim, the invention may be practiced otherwise than as specifically described.

I claim:

In a pressure gauge formed of a housing having a pressure inlet for receiving pressure from a source exteriorly of the housing, the improvement in a pressure indicating tube assembly located within the housing which compises,

(a) a Bourdon tube having one open end communicating with said pressure inlet and having a tapered end disposed generally opposite said inlet providing a confined opening,

(b) an attachment tube for said Bourdon tube having an open end and a closed end and a diameter therewith providing a substantially continuous inner surface between the tubes,

(d) a ring connection for the tubes encircling the abutting tube ends,

(e) said Bourdon tube having elastic characteristics and a sufiiciently large diameter to be operative for indicating variationsin pressure from said source and said attachment tube having a diameter sufiiciently small to be substantially unaffected by pressure and (f) said attachment tube being operable for the application of pressure for cleaning the tube assembly when its closed end is manually opened.

References Cited I UNITED STATES PATENTS 1,916,474 12/1930 French et a]. u 29-477 XR 2,469,975 5/1949 McCloy 29477 XR 2,656,723 10/1953 Heise 73--418 3,196,688 7/1965 Smith 73-418 DAVID SCHONBERG, Primary Examiner.

LOUIS R, PRINCE, Examiner.

D. O. WOODIEL, Assistant Examiner. 

